Residual stress generated in a structure causes damage such as fatigue cracks in some cases and it is important to accurately grasp the distribution of the residual stress in the structure. As a method of estimating the residual stress of a structure, there has been known a method using an inherent strain method (for example, refer to Patent Documents 1 and 2).
In a method of estimating residual stress based on the inherent strain method of the related art, two kinds of cut pieces are cut out from a structure, the elastic strain or residual stress of each cut piece is measured, and the measured value of the elastic strain or residual stress of each cut piece is applied to inverse analysis process based on a finite element method. A user inputs an assumed range in which the inherent strain is generated in the cut piece to an analysis device that performs inverse analysis process, as an analysis range. The analysis device approximates inherent strain distribution with a least squares method using a distribution function defined in the analysis range, determines the inherent strain distribution in the analysis range, and calculates the residual stress of the structure from the obtained inherent strain distribution.